Hi. And greetings from Finland.

Straigth to The point.
i Have 1997 x300 4.0L. Just got CNG natural gas system installed .
After installation CYL. 4,5,6 are running Lean even with normal fuel.. Lambdas seems to work but Fuel injectors operating voltage is about 0.2volts.
CYL. 1,2,3 had nice Brown sparkplugs and About 0.4 Volts operating voltage. Measurement done when idling from wires going inside injectors.

Can someone confirm that voltage should be about same all around and injectors operate as longer of shorter openingtime ,voltage input time changes, depending throthle opening. Voltage stays same.
Now i presume low voltage,poor injector opening.

I measured The voltage with CNG control unit and without so it seems like ECU does not give full voltage to half engine.
Or can it be the lamda sensor?
Company who did the CNG conversion had no idea how jag system work.

Need to know did they damage my ecu
as my car run fine when i got it there.

best regardsHeikki. Finland

 

The oxygen sensor would seem like a good place to start. Can you see what the live data says on your scanner?
There will be a bit of “chicken and egg” involved in considering the readings, as the lean mixture will be influencing the reading which will in turn be influencing the lean mixture.
An exhaust air leak can also cause the readings to be distorted between banks 1and 2. Suspect the richer bank of having a leak allowing air into the exhaust upstream of the oxygen sensor.

 

Hi Hege72,

All six fuel injectors should receive battery/alternator voltage (12.6 - 14 volts) on the Black wire with Light Green tracer line. These wires all connect to the ECM Controlled Relay. To test the voltage at the Black/Light Green wire, with the ignition ON or engine running, put one of your meter test leads on the B/LG wire and the other lead on a good ground (not the other injector wire). If you measure across the two injector wires, you will be measuring a very small AC voltage.





To pulse the injectors open, the ECM connects the other wire at each injector to ground (Black/Blue, Black/Slate, Black/Green, Black/Red, Black/Orange, Black/Purple).

You can download the wiring schematics at this link:

Jaguar X300 Electrical Guide 1997

If your meter has a Duty Cycle setting, you can assess whether or not the ECM is pulsing each injector equally.

Cheers,

Don

 

Hi.
Livedata shows that both oxygen sensors work about the same way tough you really had to push the pedal to see peak in live data line.
Yes exh. Air leak possible. It does not give any other signs to that direction .Sounds good i mean.
Tomorrow ill take the heatshield and do visual insp.
Thanks.

 

Hi.
Ok so there i went wrong. I had the reader connected to injectorcables. Thats why i got really low voltage readings. Tomorrow ill try as you said.
also i try to disconnect oxygensensors . Hopefully car
uses defaut map as it does not get readings from sensors. Is it runs better,it has to be oxygen sensor thats the broblem.

Thanks Don.